Electrets of organic materials are produced by applying a DC voltage to stretched films of polymers such as polyvinyl fluoride, polyvinylidene fluoride, polyvinyl chloride, polyvinylidene fluoride, polyvinyl chloride, polyacrylonitrile, polycarbonate or nylon 11, while maintaining the films at high temperature and then cooling. These films exhibit piezoelectric and pyroelectric properties.
Polymeric electret elements are useful in electro-acoustic conversion devices, electro-mechanical conversion devices, pressure-sensitive elements, bimorph elements, microwave-detection devices, image-recording light-sensitive elements, and the like.
Publications of background interest with respect to the present invention include U.S. Pat. Nos. 2,615,868 and 4,591,465, which describe copolymers of vinylidene cyanide.
There is continuing interest in the development of novel polymeric materials which exhibit improved piezoelectric and pyroelectric properties, and superior moldability and thermal stability.
Accordingly, it is an object of this invention to provide novel copolymers which exhibit piezoelectric and pyroelectric properties.
It is a further object of this invention to provide polymeric electret films which exhibit a high longitudinal piezoelectric effect.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.